SysfsGpio: add invert attribute (active-low) to the SysfsGPIO classes

The sysfsgpio resources (SysfsGPIO, NetworkSysfsGPIO and MatchedSysfsGPIO),
the GPIOSysFSExport, the driver GpioDigitalOutputDriver and the
GpioDigitalOutput agent have been modified to have an additional optional
invert (active-low) attribute (default False) which can be used to
invert the logical value used on the gpio line.

Signed-off-by: Perry Melange <isprotejesvalkata@gmail.com>

Author: pmelange

labgrid/driver/gpiodriver.py

@@ -37,9 +37,9 @@ def on_deactivate(self):
     @Driver.check_active
     @step(args=['status'])
     def set(self, status):
-        self.proxy.set(self.gpio.index, status)
+        self.proxy.set(self.gpio.index, self.gpio.invert, status)
 
     @Driver.check_active
     @step(result=True)
     def get(self):
-        return self.proxy.get(self.gpio.index)
+        return self.proxy.get(self.gpio.index, self.gpio.invert)

labgrid/remote/exporter.py

@@ -642,16 +642,19 @@ def _get_params(self):
         return {
             "host": self.host,
             "index": self.local.index,
+            "invert": self.local.invert,
         }
 
     def _get_start_params(self):
         return {
             "index": self.local.index,
+            "invert": self.local.invert,
         }
 
     def _start(self, start_params):
         """Start a GPIO export to userspace"""
         index = start_params["index"]
+        invert = start_params["invert"]  # pylint: disable=unused-variable
 
         if self.export_path.exists():
             self.system_exported = True

labgrid/resource/base.py

@@ -42,5 +42,7 @@ class SysfsGPIO(Resource):
     """The basic SysfsGPIO contains an index
 
     Args:
-        index (int): index of target gpio line."""
+        index (int): index of target gpio line.
+        invert (bool) : optional, whether the logic level is inverted (active-low)"""
     index = attr.ib(default=None, validator=attr.validators.instance_of(int))
+    invert = attr.ib(default=False,  validator=attr.validators.instance_of(bool))

labgrid/resource/remote.py

@@ -340,6 +340,7 @@ class NetworkSysfsGPIO(NetworkResource, ManagedResource):
 
     """The NetworkSysfsGPIO describes a remotely accessible gpio line"""
     index = attr.ib(validator=attr.validators.optional(attr.validators.instance_of(int)))
+    invert = attr.ib(default=False, validator=attr.validators.instance_of(bool))
     def __attrs_post_init__(self):
         self.timeout = 10.0
         super().__attrs_post_init__()

labgrid/resource/udev.py

@@ -778,8 +778,10 @@ class MatchedSysfsGPIO(USBResource):
     """The MatchedSysfsGPIO described a SysfsGPIO matched by Udev
 
     Args:
-        pin (int): gpio pin number within the matched gpiochip."""
+        pin (int): gpio pin number within the matched gpiochip.
+        invert (bool): optional, whether the logic level is inverted (active-low)"""
     pin = attr.ib(default=None, validator=attr.validators.instance_of(int))
+    invert = attr.ib(default=False, validator=attr.validators.instance_of(bool))
     index = None
 
     def __attrs_post_init__(self):

labgrid/util/agents/sysfsgpio.py

@@ -2,6 +2,7 @@
 This module implements switching GPIOs via sysfs GPIO kernel interface.
 
 Takes an integer property 'index' which refers to the already exported GPIO device.
+Takes a boolean property 'invert' which inverts logical values if set to True (active-low)
 
 """
 import logging
@@ -23,7 +24,7 @@ def _assert_gpio_line_is_exported(index):
         if not os.path.exists(gpio_sysfs_path):
             raise ValueError("Device not found")
 
-    def __init__(self, index):
+    def __init__(self, index, invert):
         self.gpio_sysfs_value_fd = None
         self._logger = logging.getLogger("Device: ")
         GpioDigitalOutput._assert_gpio_line_is_exported(index)
@@ -41,6 +42,10 @@ def __init__(self, index):
         gpio_sysfs_value_path = os.path.join(gpio_sysfs_path, 'value')
         self.gpio_sysfs_value_fd = os.open(gpio_sysfs_value_path, flags=(os.O_RDWR | os.O_SYNC))
 
+        gpio_sysfs_active_low_path = os.path.join(gpio_sysfs_path, 'active_low')
+        with open(gpio_sysfs_active_low_path, 'w') as active_low_fd:
+            active_low_fd.write(str(int(invert)))
+
     def __del__(self):
         if self.gpio_sysfs_value_fd:
             os.close(self.gpio_sysfs_value_fd)
@@ -68,24 +73,22 @@ def set(self, status):
 
         os.write(self.gpio_sysfs_value_fd, binary_value)
 
-
 _gpios = {}
 
-def _get_gpio_line(index):
+def _get_gpio_line(index, invert):
     if index not in _gpios:
-        _gpios[index] = GpioDigitalOutput(index=index)
+        _gpios[index] = GpioDigitalOutput(index=index, invert=invert)
     return _gpios[index]
 
-def handle_set(index, status):
-    gpio_line = _get_gpio_line(index)
+def handle_set(index, invert, status):
+    gpio_line = _get_gpio_line(index, invert)
     gpio_line.set(status)
 
 
-def handle_get(index):
-    gpio_line = _get_gpio_line(index)
+def handle_get(index, invert):
+    gpio_line = _get_gpio_line(index, invert)
     return gpio_line.get()
 
-
 methods = {
     'set': handle_set,
     'get': handle_get,